.banner {
    position: relative;
    width: 1200px;
    height: 350px;
    margin: 0;
    padding: 0;
}

.banner ul {
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: row;
    justify-content: center;
    width: 100%;
    height: 350px;
}

.banner_1{
    display: list-item;
    
}
.banner_2{
    display: none;
}
.banner_3{
    display: none;
}

.banner a {
    display: inline-block;
    width: 60px;
    height: 60px;
    position: absolute;
    /* z-index: 1; */
}

#left {
    left: 10px;
    top: 145px;
    background: url(../img/btn2.png) 0px 0px;
}

#right {
    right: 10px;
    top: 145px;
    background: url(../img/btn2.png) 60px 0px;
}